Problem: What is $30\%$ of $500$ ?
Explanation: Having $30\%$ of something means that you get $30$ out of every $100$ We can set up a proportion to find out what number is $30\%$ of $500$ $ \dfrac{{\text{percent}}}{100} = \dfrac{{\text{part}}}{{\text{whole}}}$ Which things do we know, and what are we trying to find? We know the ${\text{percent}}$ is $30$ . Is $500$ the ${\text{part}}$ or the ${\text{whole}}$ The $500$ is the ${\text{whole}}$ . We are trying to find the ${\text{part}}$ that makes up $30\%$ of it: $ \dfrac{{30}}{100} = \dfrac{{\text{part}}}{{500}}$ If we multiply the denominator of the fraction on the left by $5$ , it will be the same denominator of the fraction on the right. To keep things equal, let's also multiply the numerator on the left by $5$ $ \dfrac{{30} \times 5}{100 \times 5} = \dfrac{{\text{part}}}{{500}}$ $ \dfrac{{150}}{500} = \dfrac{{\text{part}}}{{500}}$ $ {150} = {\text{part}}$ So $150$ is $30\%$ of $500$.